Make filter tail-recursive

2014-06-26 18:40:40 +09:00
parent 7b1cc27b08
commit 5b215eb57a
1 changed files with 2 additions and 6 deletions
@@ -402,12 +402,8 @@
  ;; filter partition remove
  ;; filter! partition! remove!
  (define (filter pred list)
-    (if (null? list)
-        '()
-        (if (pred (car list))
-            (cons (car list)
-                  (filter pred (cdr list)))
-            (filter pred (cdr list)))))
+    (let ((pcons (lambda (v acc) (if (pred v) (cons v acc) acc))))
+      (reverse (fold pcons '() list))))

  (define (remove pred list)
    (filter (lambda (x) (not (pred x))) list))